Today I learned… in code

A lot happens between "Hello World" and "Supreme Master Programmer". Here, we share little discoveries made along the way. The more frustrating something was, the more likely it is to end up here on this site!

Heaps, AVL trees, hash tables, and a whole bunch of ways to sort data – you’ll do it all in CS261, but you might finish the course wondering why.

CS261 Review

This class is all about data structures. Some colleges combine data structures and algorithms into one semester-long class, so I’m happy that Data Structures got its own dedicated 10 weeks in OSU’s program.

Some of your new friends in CS261

Class structure

10 weeks

6 assignments total, evenly distributed through the quarter

Proctored midterm, proctored final

Nice slow-down in assignments and workload as midterm and final approach, giving sufficient time to study

Weekly group obligation: 2-5 worksheets to submit as a group (however you divvy it up is up to you) and typed weekly meeting minutes

Steady, even workload

The first 4 weeks will revisit topics from CS162, so if you wanted more practice reversing a linked list or resizing an array, you’ll get to do those things again in CS261.

After the midterm, the class spends 1 week on each topic: AVL trees (including tree sort), min heaps (including heap sort), hash tables (open addressing and chaining), and graphs (including Dijkstra’s). Big-O complexity is also covered in the context of the aforementioned subjects.

The video lectures are decent but to truly understand these topics I recommend searching the Interwebs for additional resources. These are big topics and there are many excellent explanations, diagrams, walkthroughs, etc. available on YouTube. (This is just one of them.)

The workload is consistent and gets lighter before the midterm and final, which left plenty of time to dedicate to studying for the exams.

CS261 books: the one they tell you to get, and the one you SHOULD get

I love a good book. The books we used for CS161, CS162, and CS225 were excellent. I did not love the lack of a book in CS261.

Instead of a book, CS261 provides pdfs to read every week. They are dry, boring, and do not display well on a mobile device. There are also worksheets that open with several paragraphs of reading. These are also dry, boring, and do not display well on a mobile device.

For some reason, this is the recommended (but optional) book for CS261: C Programming Language. It’s an okay book, but it’s almost completely beside the point of the class. It’s a reference to the C language. I don’t know why they recommend it – none of the class material relates back to it. If you’ve taken CS161/CS162/CS165, you know enough C++ to hobble along in C until you get your footing. If you run into any trouble (and you probably won’t past the second week or so) you’ll Google your error message, figure it out, and be on your way.

Then, at the end of fall quarter, I joined the CS325 Slack channel in preparation for my Winter 2018 quarter. There, I saw someone recommending the book Grokking Algorithms to incoming CS325 students.

THIS is the book you should buy for CS261.

I ordered it to get a jump start on CS325, but when I opened it my heart sank a bit: where the F*** was this book when I was still in CS261?!

Every section of this book is concise and clear, with simple explanations and memorable illustrations. Most topics get multiple explanations and diagrams. The book covers so many topics and I’m just kicking myself for not having this book while I was still in CS261.

Grokking Algorithms has everything from visualizing Big-O runtimes…

to performing a search on a graph…

to adding neighbors as you traverse nodes on a graph…

to sorts, complete with graphs, Big-O complexities, and pseudocode…

to understanding how the stack can be used to perform a set of instructions recursively.

This is just a small sampling of what’s in this amazing book.

I wish someone had told me about this book before I waded through CS261’s long, tedious PDFs on these subjects (which often felt like they were written for people who already understood the topic).

Do yourself a favor. If you are about to take CS261, get this book and refer to it often. It is way better than the materials they provide you in the class.

CS261 uses C, not C++

I’m pointing this out because I see a lot of questions (and complaints) about the switch to C from C++ in CS261. It’s true: unlike CS161 and CS162, CS261 assignments use the C language. HOWEVER – it’s really not a big deal. Any panicky feelings you may have over this at the start of the course will soon pass.

Instead of this:

for (int i = 0; ...)

you’ll do this:

int i;
for (i = 0; ... )

And you’ll write comments like this:

/* comment goodies here */

Little things. Nothing you can’t solve with a quick Google query and by the 2nd or 3rd week you’ll probably forget you even went through this.

They ask you to use an IDE… but you don’t need to

This surprised me: CS261’s first week includes an assignment in which you bring your code into an IDE and then submit a screenshot to show you did it.

As far as I could tell, there’s no reason to keep using the IDE past week 1. You don’t have to choose a particular IDE (or an IDE at all) for the sake of CS261. The class doesn’t teach you how to use the features that make an IDE worth using, like using the IDE’s debugger to step through code.

I tried CodeBlocks for a week, but it crashed so often it was a serious roadblock to productivity until I dumped it and went back to Sublime Text. (I’m on a Mac and the last release of CodeBlocks is from 2013 – maybe that was part of the problem.)

An IDE is just a tool, and I feel like which IDE you choose is a personal choice and none of the school’s business unless the class is going to teach specific features of that IDE or provide workflow tools that only work with the IDE, which CS261 does not. There’s no reason you should have to abandon whatever tools you’re already comfortable with. This was a strange requirement, in my opinion.

CS261 assignments

The 6 assignments are like “coding madlibs” – they provide you with a collection of files and you fill in the functions that are missing code. The assignments offer little opportunity for creativity, which probably makes grading them easier but also made them more forgettable.

The real shortcoming with the assignments was the missed opportunity to tie the data structures and sorts to real world applications. The greater context of why you might choose a particular data structure or how to analyze a problem and then decide what data structure or sorting algorithm to use is, sadly, largely absent in this class’s materials.

I felt like the “fill in the blank” nature of the assignments didn’t help my brain make links between Real Life Problems and All That Code I Wrote in a Vacuum for CS261.

Here’s a ton of code I wrote. What’s it for? Getting a good grade in CS261, of course.

This “missing context” was further illustrated to me when I told a friend about the class I was taking, and he posed a question:

"Suppose you have a million images. Filenames/filesize/etc. don't matter, just the content of the image. I give you a new image and you have to tell me if you already have this image in your set. How do you figure it out? What data structures do you use?"
- my smart friend

CS261 isn’t going to prepare you for this kind of question.

The solution – and surely there’s more than one – to my friend’s question was basically to hash all the image blobs into a hash table, then hash the new image to figure out where it would go and compare it to what’s in the table. You don’t hash on filename or filesize or anything like that, because with image hashing, you want to go by the content of the pictures themselves.

CS261 group work

The weekly group work is going to be either great or a chore depending on who you get grouped with.

In the first week of the quarter everyone was assigned to a group of 5, with the sorting criteria being our time zones and general availability as noted in a spreadsheet that the instructor shared the week before class started (hope you were checking your email!).

For 10 weeks, my group was responsible for submitting 2-5 completed “worksheets” each week by end of day Sunday and a typed log of our discussion, called “meeting minutes” (basically who said what). I use the term “worksheet” loosely, some of them were solidly in “assignment” territory.

In a perfect world, your group will engage in vigorous, insightful discussion on each worksheet, leading to new insights and reinforced learning. (Some of my classmates assured me this is what they were getting out of their CS261 group experience.)

In the actual world, your group will probably struggle to find a meeting time that works for everyone and cope with weekly absences from the group meeting. Our “discussions” were rather thin – we either agreed the worksheet was easy or hard, and then kind of struggled to find anything else to talk about.

I don’t blame my groupmates, I think the worksheets just didn’t lend themselves well to discussion. There wasn’t anything controversial or debatable about the worksheet problems, just cut and dry “fill in the blank” code.

CS261 exams

The midterm and final exams for CS261 proctored, so you’ll have to go to a nearby test center or get set up with an online proctor. Both exams are 1 hour, 50 minutes long.

The midterm is coding heavy – expect to write methods in Word docs, save out a pdf for each problem, and attach them to the test. Many questions require you to download an image or attachment from the test, open it, and answer the question in the test’s text box. This was a clunky workflow and I was constantly afraid I would accidentally navigate away from the test. The final exam, however, only required one external doc to be produced and attached, and only a couple questions required opening an attachment. (Phew.)

As for what to study: study trivia. There’s a ton of trivia sprinkled throughout this course. You’ll want to memorize the runtime complexity of every sort, when to use what data structure (according to the class materials), properties of each data structure, and so on. A lot of that trivia will show up on the test. I found it helpful to make notecards of little tidbits of info that are sprinkled throughout the lectures and reading materials – they helped, but I was still caught off-guard by some of the questions.

My CS261 flash cards and worksheet organizer were invaluable.

A few final tips for CS261

Do all the worksheets yourself, even if your group comes up with some kind of “worksheet rotation”. By the time this class was done I think I’d done every worksheet at least 2 or 3 times, because they’re good practice for the tests.

Use a visualization tool. This is the one I used – it’s not perfect (I wish it showed individual steps for things like AVL rotations) but it’ll help you check your work.

Print all the worksheets. I didn’t have a printer going into this class but I quickly saw the need for one. Most worksheets provide you with function signatures and helper methods, and your job is to “fill in the blank”. Therefore, I felt it was better to have the worksheet printed in front of me so I could fill in the blanks, rather than working in an editor (or worse, a word processing doc), separated from the rest of the worksheet.

Some of my CS261 final exam prep: I redid the weekly worksheets until I had them down cold, and I printed the questions from the practice final.

Practice on paper, and get fast. The tests are, collectively, over half your grade in this class, so your performance on the exams really matters. I felt pressed for time on both exams, finishing within 5 minutes of the time limit both times. I’ve never really been one to study for tests, figuring I should’ve learned the material during the class itself, but I had to buckle down and get serious about studying for CS261. I made flash cards, practice tests, and put probably 20 hours into studying for the midterm and over 50 into studying for the final.

Knowing the code (implementations) is important, but the final exam (which is 30% of the final grade) focuses more on knowing the step-by-step behavior of altering a particular data structure. Be sure you know how to draw specific kinds of trees and how they change when a node is removed.

Join the Slack channel! Lots of my classmates could be found there every week discussing the homework and answering each others’ questions.

Get the Grokking Algorithms book. Seriously, and while you’re at it, invent a time machine and tell me about this book before I take CS261.

And… that’s it for this quarter! I’ll be in CS325 Analysis of Algorithms next quarter (Winter 2018), so be sure to say hi if you see me (Mandi) on Piazza or Slack!

Reports from other students in the program

Are you also blogging about your journey through OSU’s eCampus CS program? Leave me a comment and I’ll add a link here!

Here’s the deal: OSU’s eCampus CS degree only requires one math class. A lot of people dread it, though, because it’s their first math class in years (or decades).

However, I am happy to report that CS225 is completely doable by someone who isn’t a natural at math. You would be hard-pressed to find someone with less of a math background than me, and yet, I managed a 94% in CS225!

Behold, my math “credentials”:

I had to take algebra twice (in 8th grade, then again in 9th)

I only earned a B in sophomore year geometry despite really trying

My last high school math class was Algebra II (another B)… not pre-calc, not calc, not physics, nothing past Algebra II

My only college math class (and I do mean only) was Math 118, and it was the sort of math class you take when you are pursuing a fine arts degree

I got a single digit score on my ALEKS assessment at the start of OSU’s CS program

Not my strongest subject, by far. But I think there’s plenty of room in programming even for those of us who suck at math, so if this is you, worry not – CS225 won’t derail your dreams.

CS225 Review

This was a good class. The homework problems made sense, the pacing was good, and the test questions were (mostly) recycled from the book, homework, and practice quizzes. The instructor seems to run the whole thing on autopilot but I didn’t need to contact her for anything.

There’s only a handful of homework questions due each week, but potentially dozens more you can do from the book and “last quarter’s homework” if you want. (I did all the extra work, and I think it really paid off at test time.)

Good news: this didn’t happen in CS225!

Class structure:

10 weeks

2 homework assignments per week

1 quiz per week (7 total, no quizzes before/after midterm and none in the final week)

1 midterm around week 6

1 final in week 10

The tricky part about this class is the grade weighting. 90% of the grade is from quizzes and tests. The midterm is worth 30%, the final is worth 30%, and your 6 best-score quizzes are worth 30% (collectively). The homework is a mere 10% of your final grade. Since both the midterm and the final are proctored, you do have to know your stuff inside and out before you sit down to take the exam.

Fortunately, nearly all of the test questions were outright copies of, if not very similar to, questions you would have seen in the homework and practice quizzes.

If there’s anything this class isn’t so good at, it’s the video lectures. (Seems none of these OSU courses so far have decent videos.) On the bright side, YouTube is bursting with math enthusiasts who have made short, memorable videos on every topic this class will cover.

My little CS225 algebra prep guide

Many people ask online what they should study in preparation for CS225. I think the ALEKS modules are complete overkill. I found myself Googling these seemingly basic concepts that I completely forgotten in the 15 years since my last math class:

factorials – what does 5! mean?

adding fractions – a/b + c/d = ?

multiplying fractions – a/b * c/d = ?

dividing fractions – (a/b)/(c/d) = ?

factoring these things – (2a + 1)(a + 2)

And that’s it. The rest you can pick up in the class itself.

More CS225 tips

Here are my general tips for succeeding in CS225.

Do the extra assignments, too

Every week has the homework that’s required, and then a larger set of extra questions that are just for your own edification. I did those extra problems and found them worthwhile come test time. I also did all the practice quizzes.

Get a Chegg subscription

I never heard of chegg.com before I took this class (I found it through Googling my questions). $15/month gets you unlimited access to the book’s answer key. Not because you’re going to copy the answers and blow off the homework, no – you need to know what you’re working towards on every question you tackle. How else will you know if you got it right? :D

Warning: not every single answer is in Chegg. I think I found maybe 4 of my assigned problems that were just blank in Chegg. But.. chances are if you Google the problem, someone on the math Stack Exchange or their own blog has posted a solution. Or you can solve a different but similar one that does have an answer, and then take a pretty good guess at the one you’ve been assigned.

Get the physical copy of the book

Yes, this is the most expensive book of the entire program, but you can buy it used on Amazon (which is how I got mine, and the book was in great shape).

A physical copy is great. It’s easier to jump around in than a .pdf, you can sticky note various topics, and you can take it with you and study in more places! I also rented a .pdf version of the book, but it didn’t display well on my tablet or my phone.

Study hard for the tests – and attempt every question

The two proctored exams are 60% of your grade (30% is your 6 quizzes, 10% is the weekly homework). Some of the questions are taken word for word from the book or homework.

Here’s a hint: simply attempting an exam question is worth a lot of points. Every exam question is worth 10 points and they’re ‘free form’ (you type in a box, not multiple choice). Even if you can’t (or don’t have time to) solve it, explaining what you would do to solve it can get you 7/10 or more points on the problem. Therefore, the winning-est strategy is to pace yourself such that you have enough time to at least lay out the basics of your answer to every question.

I ran out of time on the midterm and had to slap together half-baked responses to the last three questions. However, since I was able to type out what I would do if I had more time, and still ended up with a 93% on the test. Phew!

I took the class by itself

I’m on the 4-year track and while CS225 is popular to pair with CS161, I’m glad I took it by itself. As I said earlier, I am not the greatest at math – so taking the class by itself helped me have plenty of time to dedicate to extra problems, studying for exams, and re-watching the same videos until I felt like I understood the topics.

And.. that’s it! My next class starts in autumn, so I’ll report back on my OSU studies in December.

The beatings are over I survived CS162! If you were wondering where OSU’s eCampus computer science weeder course is, this is it.

The material is challenging and the workload is punishing. The video lectures are crap, but the book is good. The class isn’t well organized (expect poorly written assignments with unclear requirements). 10 weeks is nowhere near enough.

However: I learned a lot. I got faster than I ever thought possible and worked with topics I thought would have had their own standalone courses.

In this article: topics covered in CS162, survival guide, what I thought of the class.

Equipment

CS162 is a programming class. Like CS161, I found my Macbook to be sufficient for this class.

I don’t know why they tell people to get a Windows PC and use Visual Studio. I didn’t need it and you won’t need it – there is no assignment based on Visual Studio knowledge.

In fact, judging just by Piazza posts, a number of students seemed confused by the extra files and the “another thing to learn” factor introduced by Visual Studio.

In case you are curious: I did every assignment in Sublime Text and a Terminal window.

Workload

At any given time expect to be working on a 1-week lab assignmentand a 2-week project, and mid-course, a group project on top of the first two. You will also write a multi-page document (PDF) for each project with a test plan (input, expected outcome chart), your designs, ideas you changed along the way, reflections on the assignment. This document always took me at least 3-5 hours to complete to my standards. There’s a quiz every couple weeks (15 minutes, not proctored).

I’m a proactive student who started each week’s material the moment it was released, worked on it daily, and generally finished just moments before a new load of work was dumped onto me.

The first two weeks hit like a ton of bricks: a simple Langton’s Ant simulation by itself would have been a large assignment, but CS162 adds a user-navigable menu, input validation, user-adjustable parameters (dynamically sized board, variable turns to run, etc.), and other features that have to be designed, coded, tested, debugged.

Oh, yeah – it has a visual component, too.

There are also two lab assignments to complete while you work on the Langton’s Ant project.

This pattern continues until the end of the course. The toughest week was the one where I was working on a project, a lab, and a group assignment all at the same time.

Here’s what I did (or wish I’d done sooner) that made CS162 more bearable.

Take it by itself (if you can)

I know there are financial aid reasons not to but if you’re normally taking 2 classes a quarter, consider taking CS162 alone (or at least with fewer classes than you normally would). It’s a ton of complex material – assuming you haven’t worked a lot with C++ pointers, memory, arrays, etc. yet – and the assignments are black holes for time.

Diagram things out on paper

I found many of CS162’s assignments too complex to hold entirely in my brain.

For example, here’s a crazy thing we did: create a circularly linked list (in C++), let the user fill it and delete nodes from it. When you exit the program, it has to unload from memory node by node. “Empty nodes” are marked with -1 for their values. This drawing I made helped a ton (actually, this was probably the 5th iteration of this drawing).

And here’s another one, this one showing how the heroes in the polymorphism project either rejoin the tournament queue or get kicked out to each player’s respective loser pile.

PS: Some people got really precious about their diagrams having to be works of art, but you don’t have to for these assignments. Just draw this stuff out, paper/pencil (or a little whiteboard) is sufficient, and plan to trash your first few drawings. If you need some material to bulk out your retrospective writing assignments for each project, photos of the diagrams you make are excellent fodder.

Go straight to Google (and Stack Overflow, and YouTube)

Sure, it sucks to pay $1880 to do so much self-teaching but you’ll get a lot of mileage out of the skill. The recorded lectures are crappy and I felt like they were wasting my time. There are better guides to all of the concepts covered in this class on YouTube.

I recommend getting a physical copy so you can have it open next to your computer while you work, and use your monitor(s) for your code and Stack Overflow. It’s the same book you use for CS161 (if you haven’t taken that yet, either), so at least you get two classes out of it. You can also buy the loose leaf edition to save some cash.

After two classes with it I can say it’s a good book. The examples are relevant to the coursework, they’re clear and easy to understand, and there are a good number of examples.

Start every week’s material the day it drops – and don’t count on weekends

Sometimes the new week will be released on a Friday. Sometimes a Saturday. Sometimes a Sunday! And no, the instructor doesn’t move that week’s deadline out just because you lost the weekend due to the materials not being released in a timely manner.

For this reason, I recommend setting up your life (at least for these 10 weeks) to allow for working on this class work during the week (ideally daily). Don’t expect to fit it all into the weekend. Even my light weeks were at least 15 hours spent on the class (usually closer to 25 or 30).

Check Piazza religiously

If they improve anything in CS162, I hope it’s the unclear assignment requirements. They requirements were notoriously bad – assignments are written in a conversational style and it’s hard to know what is really being asked for.

Many students took to Piazza (the class forum) to question (or worse, debate) the requirements until a TA or the instructor herself came along to clarify.

Pretty much every week went like this:

New assignment comes out – oh no, it has unclear requirements

Someone asks for clarification on Piazza

TA makes a call and says do it X way

2 days later, another student asks the same question

Different TA makes a different call on this new thread and says do it Y way

They have a fight, triangle wins…

You already coded it, so do you redo it to Y or keep it as X or what?

For what it’s worth, every time this happened (and I had already coded it), I kept my code the original way and still got 100% on the assignment.

Test on Flip!

So many things happened in my code in the Flip environment that did not happen on my Macbook. Weird things, too – things that weren’t easy to spot without thorough testing. I made the mistake of not testing on Flip until I thought I was done with the assignment, only to find heaps of bugs that only occurred in that environment.

It’s a memory management tool that’s already installed on Flip and you won’t be able to find memory leaks without it. If you wait until you are done coding your assignment, it will be harder to find the memory leak. Upload your code and check it with Valgrind every so often and you will save yourself a lot of pain.

The worst weeks were weeks 1, 2, and the final project.

Okay, they were all brutal. There were many weeks where I thought there was no way I would get everything done and I’m a workaholic. The biggest workloads were the first project (Langton’s Ant) and the final project at the end (make an adventure game).

You do actually have to contribute to the Canvas conversation topics

It’s a misguided requirement because these “conversation” threads quickly turn into 100+ people dumping commentary and links in one place. It’s not a conversation, it’s just a dogpile.

But if you contribute a few posts (I think I made 5 decent, paragraph-sized comments between January and March, evenly spaced throughout the quarter), it’s an easy 20 points that you will (probably) be very happy to have at the end.

Take every quiz twice

(Unless you get a great score the first time around, of course).

You get two attempts for each quiz. A quiz is 20 questions in 15 minutes. (I liked this format). Only the grade from the last attempt is kept. Questions are drawn from a larger pool, so you won’t get exactly the same ones the second time you take it.

My strategy was to use the first attempt to see what’s on the quiz and make my best guesses as to the answers. This gave me a feel for the questions and sometimes revealed tricky ones. I usually got about a 16/20 on my first try but Canvas tells you which ones you got wrong, and what the correct answers were, so this is a chance to see what you missed and study it some more. After a little studying I’d retake it, usually getting 18/20 or 19/20 that second time.

Grading

The final’s worth 15% of your grade, so save some steam for the end. There was a bonus, extra credit lab announced right at the last minute, too, but its points could only be applied to your lab grade.

Weekly labs – 30% of your grade

Quizzes – 15% of your grade

Projects – 30% of your grade

Group activities – 10% of your grade

Final project – 15% of your grade

Overall impression: OSU CS162

I hated it at times, but it was worth it. I never would have pushed through some of this stuff on my own, without a grade and a degree motivating me. OSU’s online CS is meant for people with a full-time job and the occasional signs of life outside of class but I had to take a couple days off work here and there to accommodate the workload, and I barely saw my family. The most difficult parts of this class – deciphering confusing and unclear requirements – were totally unnecessary. OSU should hire a proofreader and clean up CS162’s assignments. And some weeks the workload was just pure insanity – the week with the group project stands out in particular.

But… it’s over! And I got a 97%, so I’m going to take a much-deserved week to rest up for the next class.

The “Student Value Edition” is significantly cheaper than the usual version. But it had no reviews, and I couldn’t find anyone else talking about it online, so I was kind of hesitant to order it.

(I ordered it anyway.)

I’m happy to report that this book is the real deal.

It arrived 3 days after I ordered it. It’s basically an unbound stack of papers 1.5 inches thick. Nothing holds it together except for the plastic sleeve it arrives in.

Other than that, though, it’s exactly the same content you’d get with an actual binding and cover. It’s in color, printed on both sides, and the individual pages are thin(ish) but probably no thinner than what’s in the actual book.

And there you have it – a slightly more affordable way to get CS 161’s book in paper format.

As for the book’s actual content, I’ll be working through it over the next 11 weeks and I’ll let you all know what I think. I’ve read the first two chapters and it looks like it’ll be a solid introduction to computer science fundamentals textbook.